scm/autochange.scm

   1
   2
   3 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
   4 ;; autochange - fairly related to part combining.
   5
   6 (define-public (make-autochange-music music)
   7   (define (generate-split-list change-moment event-list acc)
   8     (if (null? event-list)
   9         acc
  10         (let* ((now-tun (caar event-list))
  11                (evs (map car (cdar event-list)))
  12                (now (car now-tun))
  13                (notes (filter (lambda (x)
  14                                 (equal? (ly:music-property  x 'name) 'NoteEvent))
  15                               evs))
  16                (pitch (if (pair? notes)
  17                           (ly:music-property (car notes) 'pitch)
  18                           #f)))
  19           ;; tail recursive.
  20           (if (and pitch (not (= (ly:pitch-steps pitch) 0)))
  21               (generate-split-list #f
  22                                    (cdr event-list)
  23                                    (cons (cons
  24
  25                                           (if change-moment
  26                                               change-moment
  27                                               now)
  28                                           (sign (ly:pitch-steps pitch))) acc))
  29               (generate-split-list
  30                (if pitch #f now)
  31                (cdr event-list) acc)))))
  32
  33   (set! noticed '())
  34   (let* ((m (make-music 'AutoChangeMusic))
  35          (context (ly:run-translator (make-non-relative-music music) part-combine-listener))
  36          (evs (last-pair noticed))
  37          (split (reverse! (generate-split-list
  38                            #f
  39                            (if (pair? evs)
  40                                (reverse! (cdar evs) '()) '())
  41                            '())
  42                           '())))
  43     (set! (ly:music-property m 'element) music)
  44     (set! (ly:music-property m 'split-list) split)
  45     (set! noticed '())
  46     m))